It Takes Nearly Twice as Long to Stop from 80 MPH vs. 60 MPH. Here's Why.

Let's do a thought experiment. Imagine you're reading about a new sports car, the Gorgonzola MVS-400istxC Black Edition. This stellar performance vehicle has the world's best brakes: A 60-0 panic stop takes just 60 feet. Pop quiz: How much distance does it take to stop from 80 mph?

If you guessed 80 feet, you're dead wrong. It all has to do with a tricky little aspect of physics—one that most car enthusiasts know nothing about.

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See, if you got this brain-teaser wrong, it's probably because you thought the stopping distance increases proportional to speed. Eighty mph is one-third faster than 60 mph; therefore, you may have told yourself, the stopping distance from 80 should be one-third longer.

But that's never the case. Take a look at the braking data on the McLaren 720S, our 2018 Performance Car of the Year: Stopping from 60 mph takes 108 feet, while from 80 mph it takes a full 178 feet. That's nearly 65 percent more distance, far greater than the 33.3-percent increase in speed.

Look up the braking distances of any car, new or old, fast or slow. It doesn't matter if it's got giant carbon-ceramic brakes, the world's most advanced ABS, and the stickiest tires known to man. Every car's 80-0 braking distance will be well over 50 percent longer than its 60-0.

Why? It all has to do with physics. See, braking distance measures how a vehicle turns kinetic energy (forward motion) into thermal energy (the heat given off by the brakes). And as a car's speed increases, its energy increases even faster. To calculate a moving car's energy, you square the speed.

To see exactly how this calculation works, check out this explanation by YouTube's Numberphile. Using nothing more than a sheet of blank paper and a doodle of two cars going different speeds, Numberphile shows you why a small increase in speed leads to a big increase in stopping distance.

Think about this the next time you're on the race track, or hurtling down your favorite abandoned road. As your speed increases, your stopping distance increases by the square of your speed. That adds up to a lot when you're barreling toward some sort of immovable object.

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